The Kumaraswamy generalized gamma distribution with application in survival analysis

We introduce and study the so-called Kumaraswamy generalized gamma distribution that is capable of modeling bathtub-shaped hazard rate functions. The beauty and importance of this distribution lies in its ability to model monotone and non-monotone failure rate functions, which are quite common in lifetime data analysis and reliability. The new distribution has a large number of well-known lifetime special sub-models such as the exponentiated generalized gamma, exponentiated Weibull, exponentiated generalized half-normal, exponentiated gamma, generalized Rayleigh, among others. Some structural properties of the new distribution are studied. We obtain two infinite sum representations for the moments and an expansion for the generating function. We calculate the density function of the order statistics and an expansion for their moments. The method of maximum likelihood and a Bayesian procedure are adopted for estimating the model parameters. The usefulness of the new distribution is illustrated in two real data sets.     

Survival and lifetime data analysis with a flexible class of distributions

We introduce a general class of continuous univariate distributions with positive support obtained by transforming the class of two-piece distributions. We show that this class of distributions is very flexible, easy to implement, and contains members that can capture different tail behaviours and shapes, producing also a variety of hazard functions. The proposed distributions represent a flexible alternative to the classical choices such as the log-normal, Gamma, and Weibull distributions. We investigate empirically the inferential properties of the proposed models through an extensive simulation study. We present some applications using real data in the contexts of time-to-event and accelerated failure time models. In the second kind of applications, we explore the use of these models in the estimation of the distribution of the individual remaining life.     

Testing Inference in Inflated Beta Regressions under Model Misspecification

We consider testing inference in inflated beta regressions subject to model misspecification. In particular, quasi-z tests based on sandwich covariance matrix estimators are described and their finite sample behavior is investigated via Monte Carlo simulations. The numerical evidence shows that quasi-z testing inference can be considerably more accurate than inference made through the usual z tests, especially when there is model misspecification. Interval estimation is also considered. We also present an empirical application that uses real (not simulated) data.     

Comparing two types of navigational interfaces for Virtual Reality

Previous studies suggest significant differences between navigating virtual environments in a life-like walking manner (i.e., using treadmills or walk-in-place techniques) and virtual navigation (i.e., flying while really standing). The latter option, which usually involves hand-centric devices (e.g., joysticks), is the most common in Virtual Reality-based studies, mostly due to low costs, less space and technology demands. However, recently, new interaction devices, originally conceived for videogames have become available offering interesting potentialities for research. This study aimed to explore the potentialities of the Nintendo Wii Balance Board as a navigation interface in a Virtual Environment presented in an immersive Virtual Reality system. Comparing participants' performance while engaged in a simulated emergency egress allows determining the adequacy of such alternative navigation interface on the basis of empirical results. Forty university students participated in this study. Results show that participants were more efficient when performing navigation tasks using the Joystick than with the Balance Board. However there were no significantly differences in the behavioral compliance with exit signs. Therefore, this study suggests that, at least for tasks similar to the studied, the Balance Board have good potentiality to be used as a navigation interface for Virtual Reality systems.     

How do industry and country impact firm performance? A national and supranational analysis

We contribute to the literature of the country, industry and firm effects on performance by developing an autoregressive cross-classified mixed-effect linear model that examines heterogeneity in the profitability of corporations in emerging and developed economies, as well as corporations located in different supranational regions. To this purpose, we simultaneously decompose abnormal returns into permanent and transitory components at the firm, industry, country and industry–country levels. We find that firms in emerging countries have significantly higher rates of performance persistence and different sources of persistence compared to firms located in developed countries. These differences are also evident between different supranational regions and countries at different levels of institutional development.

     

Exposure to Traffic and Risk of Hospitalization Due to Injuries

Research on the risk of motor vehicle injuries and their relationship with the amount of travel has been only partially analyzed. The few individual exposure assessments are related to very specific subsets of the driving and traveling populations. This study analyzes the relationship between kilometers traveled and hospitalization due to motor vehicle injuries. Twelve thousand three hundred and sixty nine Spanish university graduates from the Seguimiento Universidad de Navarra multipurpose cohort study were evaluated. They had not been hospitalized due to motor vehicle injuries at baseline and were followed up to eight years. Biannual questionnaires allowed for self‐reporting of kilometers traveled in motor vehicles, together with incidence of hospitalization. Covariates in the Cox regression models included age and gender and baseline use of safety belt while driving, driving a vehicle with driver‐side airbag, driving a motorcycle, and drinking and driving. There were 49,766 participant‐years with an average yearly travel of 7,828 km per person‐year. Thirty‐six subjects reported a first hospitalization event during this time. The adjusted hazard ratio per additional kilometer traveled was 1.00005 (95% confidence interval 1.000013 to 1.000086). Even the smallest of reductions in the amount of kilometers traveled (from an average of 3,250 km per year to 1,000) has a statistically significant protective effect on the likelihood of sustaining hospitalization due to motor vehicle injury (aHR 0.9, 95% CI 0.78 to 0.98). In light of current policies aimed to reduce motorized traffic due to environmental concerns, it may be appropriate to consider the additional health benefit related to reductions in injuries.     

Freedom,Identity, and the Social History of Empire in Atlantic Cuba, 1795–1817

This essay examines a maritime case involving a Charleston-based French privateer in 1795 as well as members, subjects, and citizens of multiple societies from Western Africa, Cuba, Spain, and Great Britain in order to reveal the fluid legal foundations of trans-Atlantic regimes with respect to slavery and freedom. The French maritime seizure of a British slaving vessel in the Caribbean and the subsequent transfer of enslaved African peoples from British to French to Spanish authority in Cuba set the stage for nearly 40 years of litigation in both hemispheres. The case led to legal disputes in Philadelphia, Madrid, and Havana as members of this Atlantic society sought to confront the most prominent political and social issues of this era. While officials in Philadelphia sought to avoid entanglement in the imperial wars between France and Great Britain, officials in Madrid and Havana competed with each other in order to define the legal identities of a group of Carabalí-Oru peoples onboard the British vessel. For their part, this group of Carabalí-Oru peoples exploited the ambiguities created by a system of Atlantic jurisprudence while relying on their memory of the Middle Passage in order to challenge their unjust enslavement in Cuba.     

Political election on legal retirement age

In the context of the current debate surrounding the reform of pension systems, this paper analyzes the political economy of the legal retirement age. Using a life-cycle model in which individuals differ by age and by wage, we analyze the outcome of a majority voting process on the legal retirement age in a Pay-As-You-Go pension system. The results show that the older an individual is, the closer her optimal retirement age is to the status quo age. That is, the status quo retirement age acts as a magnet. Additionally, we find that the preferred legal retirement age of most of the working population increases when the pension system is more redistributive. We also observe a positive relationship between the preferred legal retirement age and the status quo age.     

To participate or not to participate: that is the question

Do I wish to participate or not to participate in this program? That is the question that young people ask themselves when considering a new opportunity. What can be done to increase the likelihood that they will choose to participate in out-of-school-time (OST) programs? This chapter describes a qualitative study that examined reasons for participating or not participating in OST programs. Some common reasons emerged, but the study also revealed differences among youth from different ethnic groups. It is clear that those who design and conduct programs must understand the processes through which diverse adolescents initiate their participation in programs and either persist or drop out. Given the apparent benefits of active participation in youth programs, it is important to remove barriers and increase access and, equally important, design programs that are of interest to youth in the contexts in which they live.